Tarnish resistant alloy



Patented Feb. 7, 1933 UNITED STATES PATENT OFFICE ROBERT E. LEA CH, OFFAIRFIELD, CONNECTICUT, ASSIGNOR TO HANDY & HARMAN, OF NEW YORK, N. Y.,A CORPORATION OF NEW YORK TARNISH RESISTANT ALLOY Ho Drawing.

This invention relates to silver alloys and is concerned moreparticularly with a novel silver alloy which has great resistance totarnish and other discoloration and which may have varying physicalproperties depending upon the purpose for which it is to be used.

The new alloy contains a preponderatmg amount of silver, ranging forexample, from 80% to 95%, the amount of silver present depending on thepurpose for which the alloy is to be used. If desired it ma be ofsterling fineness, the term sterling being used to designate a silveralloy which contains, per thousand parts, approximately 925 parts ofsilver and the remainder of base metal. Sil ver alloys as customarilymade include copper as the base metal and such alloys are subject todiscoloration which may be due to the action of -various substancescontained in dilute form in the atmosphere, or in the case of tableware,the discoloration or tarnish may result from exposure of the ware to theaction of fruit acids, or contact with foods containing sulphur invarious forms and other substances which contain ingredients which reactwith the silver.

It is the object of my invention to provide a silver alloy which resistsdiscoloration and corrosion, and I accomplish this result bysubstituting for the copper ordinarily used as the base metal in such analloy, cadmium and nickel.

, When cadmium is added to silver, there is produced a ver ductile whitealloy which can be worked y rolling, spinning and the like to asubstantially greater extent than the ordinary silver-copper alloy,without becoming hard. Apparently the cadmium forms with the silver ahomogeneous alloy of uniform quality and satisfactory in many respectsas, for example,

in its tarnish-resisting qualities, but such an alloy is usually so softthat an article made from it and produced with little working of themetal is comparatively soft and is not sufiiciently resistant todeformation and marring for ordinary purposes. Such an article,therefore, is likely to become readily dented or bent in service and isobjectionable for that reason.

I have found that silver and nickel alone Application filed January 19,1931. Serial No. 509,885.

do not make satisfactory alloys but when nickel and cadmium are combinedwith silver in an alloy, the nickel apparently contributes to thetarnish-resisting qualities of the combination and at the same timealters the mechanical properties so that by proper selection of theproportions of these three ingredients, it is possible to produce analloy having the desired tarnish-resisting qualities and the ductilityand malleability desired for spe cific purposes. I

An alloy, which has the desired tarnish-resisting as well as mechanicalproperties, made in accordance with this invention contains apreponderating amount of silver and relatively small amounts of cadmiumand nickel. The silver may run from 80% to 95%, for example, with thecombined amounts of cadmium and nickel not exceeding one-quarter of theamount of the silver, or 20% of the total. The cadmium may run fromapproximately 4.9% to 19.9%, while the nickel may vary from 0.1% to 2%.Under ordinary circumstances, the amount of cadmium present will be inexcess of the amount of nickel.

An alloy containing cadmium approaching the upper limit is likely to becomparatively soft and ductile and may therefore be best used in theproduction of articles in which considerable working is required. Forproduction of articles requiring little working, the alloy used willhave less cadmium andmore nickel. A noticeable hardening effect may beobtained with as little as 0.1% nickel, provided the cadmium present isrelatively small in amount, and for ordinary purposes the nickel will berelatively small in amount not to exceed 0.5% though I contemplate thatas high as 2% nickel may be used in special instances. Increasing theamount of nickel varies the physical pro erties of the alloy aspreviously indicated w ile increasing the cadmium increases theresistance of the alloy to corrosion and tarnish.

Silver which is in the greatest demand at the present time is sterlingsilver and such an alloy produced in accordance with the presentinvention may contain about 925 parts of silver per 1000 parts, from 1.0to 20 parts of nickel, and from to 7 4 parts of cadmium. Solid silvermay from a scientific standpoint be considered to contain as little as66.6% of silver but I prefer to produce the new alloy with a greaterproportion of silver and find that the best results are obtained whenthe silver runs above approximately An alloy containing the specifiedingredicuts in the proportions mentioned is found to resist corrosionand discoloration to a much greater extent than ordinary alloys whichcontain silver with copper as the base metal. Inasmuch as the mechanicalproperties of the new alloy may be varied within a substantial range byproper variation in the ingredients as indicated, the new alloy iscapable of wide use in the production of. various articles for example,tableware o'r hollow ware.

I claim:

1. An alloy containing silver ranging from 80% to nickel ranging from0.10% to 2%, and the remainder cadmium.

2. An alloy containing about 92.5% of silver, nickel from 0.10% to 2%,and the remainder cadmium.

In testimony whereof I affix my signature.

ROBERT H. LEACH.

